1. Field of the Invention
The present invention relates to a catalyst unit that includes catalyst ingredients to reduce harmful materials of exhaust gas according to a flow characteristic.
2. Description of Related Art
In a vehicle, a three way catalyst converter is generally used to purify exhaust gas, which is disposed on an exhaust pipe, and the specifications thereof are different, because exhaust gas flow rates are different according to vehicles.
The three way catalytic converter simultaneously reacts harmful materials of exhaust gas such as carbon monoxide, nitrogen oxide, and hydrocarbon compound to eliminate these materials, and mainly Pt/Rh, Pd/Rh or Pt/Pd/Rh series is formed in the three way catalytic converter.
Meanwhile, a diesel vehicle that generates large amount of noxious exhaust gas is excellent in a fuel consumption efficiency and a power output, but nitrogen oxide and PM (particulate matters) are heavily included therein in contrast to a gasoline vehicle.
In the diesel vehicle like this, because intake air is sufficiently combusted in the most of driving condition, carbon monoxide and hydrocarbon is very little compared to the gasoline vehicle and nitrogen oxide and PM is heavily exhausted.
Recently, as a post process art, a diesel particulate filter research is very actively being undergone so as to correspond to the reinforced exhaust gas standard of the diesel vehicle, and there are many parts that are to be developed so as to apply the diesel particulate filter to a real vehicle.
Platinum is used in a coating layer of a Diesel Oxidation Catalyst (DOC), separately, Diesel Particulate Filter (DPF) is applied to a system of DOC+DPF, and CPF, which is recently being mass produced in a EU vehicle maker, and the reliability thereof increased the sales of the system.
And, a diesel particulate filter that a catalyst is coated thereon, which is called a diesel catalyzed particulate filter, has been developed. Meanwhile, several methods have been widely known for coating different kinds of catalyst on a cordierite carrier, and there are many prior arts.
For example, there is a dipping method that a cordierite carrier is dipped into catalyst solutions respectively having different concentrations and there is a suction method that one end side of a carrier is dipped into a catalyst solution and a vacuum pressure is formed in the other end side of the carrier to suck the catalyst solution through channels of the carrier.
However, these methods can be applied to a wall flow type of a carrier, and more particularly, different kinds coatings can be only applied to a carrier having the wall flow type, wherein CO or HC flows into an inlet of a channel of the carrier to get out of the outlet thereof.
Meanwhile, a noble metal is coated in the whole carrier regardless of flow characteristic of exhaust gas when manufacturing the catalyst carrier, wherein there is a problem that a noble metal is not efficiently used according to the flow characteristic of the exhaust gas.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.